The estimated range highlights. Edit the range by left-clicking and dragging the cursor over all values in the row to sum, if desired. The selected rows are highlighted.

If you don't have an existing file, use the blank worksheet in Excel. Type a zero in the first row of your column and drag your mouse down to the last row of the column to autofill it with zeros.

You can't use a SUM() function to sum a filtered list, unless you intend to evaluate hidden and unhidden values. Here's how to sum only the values that meet your filter's criteria.